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Acetyl-CoA
 
 
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Acetyl-CoA is an important molecule in metabolism, used in many biochemical reactions. Its main use is to convey the carbon
Carbon

Carbon is a chemical element with chemical symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalence?making four electrons available to form covalent bond chemical bonds....
 atom
Atom

|-! bgcolor=gray | Properties|-||}The atom is a basic unit of matter consisting of a dense, central atomic nucleus surrounded by a electron cloud of electric charge electrons....
s within the acetyl
Acetyl

In organic chemistry, acetyl , is a functional group, the acyl of acetic acid, with chemical formula -CarbonOxygenCarbonHydrogen3. It is sometimes abbreviated as Ac ....
 group to the citric acid cycle
Citric acid cycle

The citric acid cycle ? also known as the tricarboxylic acid cycle ; the Krebs cycle; or, more rarely, the Szent-Gy?rgyi-Krebs cycle) ? is a series of enzyme-catalysed chemical reactions of central importance in all living cell s that use oxygen as part of cellular respiration....
 to be oxidized for energy production. In chemical structure, acetyl-CoA is the thioester
Thioester

Thioesters are compounds resulting from the bonding of sulfur with an acyl group with the general formula R-S-CO-R. They are the product of esterification between a carboxylic acid and a thiol ....
 between coenzyme A
Coenzyme A

Coenzyme A is a coenzyme, notable for its role in the Fatty acid metabolism#Synthesis and Fatty acid metabolism#.CE.B2-Oxidation of fatty acids, and the oxidation of pyruvic acid in the citric acid cycle....
 (a thiol
Thiol

In organic chemistry, a thiol is a compound that contains the functional group composed of a sulfur atom and a hydrogen atom . Being the sulfur analogue of an alcohol group , this functional group is referred to either as a thiol group or a sulfhydryl group....
) and acetic acid
Acetic acid

Acetic acid, CH3COOH, also known as ethanoic acid, is an organic acid which gives vinegar its sour taste and pungent smell. Pure, water-free acetic acid is a colourless liquid that absorbs water from the environment , and freezes at 16.7 Celsius to a colourless crystalline solid....
 (an acyl
Acyl

An acyl group is a functional group derived by the removal of one or more hydroxyl groups from an oxoacid.. In organic chemistry, the acyl group is usually derived from a carboxylic acid of the form RCarbon Oxygen hydroxyl....
 group carrier). Acetyl-CoA is produced during the second step of aerobic cellular respiration
Cellular respiration

Cellular respiration is the set of the metabolism reactions and processes that take place in organisms' cell s to convert Energy from nutrients into adenosine triphosphate , and then release waste products....
, pyruvate decarboxylation, which occurs in the matrix
Matrix (biology)

In biology, matrix is the material between animal or plant cell , the material in which more specialized structures are embedded, and a specific part of the mitochondrion that is the site of oxidation of organic molecules....
 of the mitochondria.






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Encyclopedia


Acetyl-CoA is an important molecule in metabolism, used in many biochemical reactions. Its main use is to convey the carbon
Carbon

Carbon is a chemical element with chemical symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalence?making four electrons available to form covalent bond chemical bonds....
 atom
Atom

|-! bgcolor=gray | Properties|-||}The atom is a basic unit of matter consisting of a dense, central atomic nucleus surrounded by a electron cloud of electric charge electrons....
s within the acetyl
Acetyl

In organic chemistry, acetyl , is a functional group, the acyl of acetic acid, with chemical formula -CarbonOxygenCarbonHydrogen3. It is sometimes abbreviated as Ac ....
 group to the citric acid cycle
Citric acid cycle

The citric acid cycle ? also known as the tricarboxylic acid cycle ; the Krebs cycle; or, more rarely, the Szent-Gy?rgyi-Krebs cycle) ? is a series of enzyme-catalysed chemical reactions of central importance in all living cell s that use oxygen as part of cellular respiration....
 to be oxidized for energy production. In chemical structure, acetyl-CoA is the thioester
Thioester

Thioesters are compounds resulting from the bonding of sulfur with an acyl group with the general formula R-S-CO-R. They are the product of esterification between a carboxylic acid and a thiol ....
 between coenzyme A
Coenzyme A

Coenzyme A is a coenzyme, notable for its role in the Fatty acid metabolism#Synthesis and Fatty acid metabolism#.CE.B2-Oxidation of fatty acids, and the oxidation of pyruvic acid in the citric acid cycle....
 (a thiol
Thiol

In organic chemistry, a thiol is a compound that contains the functional group composed of a sulfur atom and a hydrogen atom . Being the sulfur analogue of an alcohol group , this functional group is referred to either as a thiol group or a sulfhydryl group....
) and acetic acid
Acetic acid

Acetic acid, CH3COOH, also known as ethanoic acid, is an organic acid which gives vinegar its sour taste and pungent smell. Pure, water-free acetic acid is a colourless liquid that absorbs water from the environment , and freezes at 16.7 Celsius to a colourless crystalline solid....
 (an acyl
Acyl

An acyl group is a functional group derived by the removal of one or more hydroxyl groups from an oxoacid.. In organic chemistry, the acyl group is usually derived from a carboxylic acid of the form RCarbon Oxygen hydroxyl....
 group carrier). Acetyl-CoA is produced during the second step of aerobic cellular respiration
Cellular respiration

Cellular respiration is the set of the metabolism reactions and processes that take place in organisms' cell s to convert Energy from nutrients into adenosine triphosphate , and then release waste products....
, pyruvate decarboxylation, which occurs in the matrix
Matrix (biology)

In biology, matrix is the material between animal or plant cell , the material in which more specialized structures are embedded, and a specific part of the mitochondrion that is the site of oxidation of organic molecules....
 of the mitochondria. Acetyl-CoA then enters the citric acid cycle.

Acetyl-CoA is also an important component in the biogenic synthesis of the neurotransmitter acetylcholine
Acetylcholine

The chemical compound acetylcholine is a neurotransmitter in both the peripheral nervous system and central nervous system in many organisms including homo sapiens....
. Choline
Choline

Choline is an organic compound, classified as a water-soluble essential nutrient and usually grouped within the Vitamin B complex. This natural amine is found in the lipids that make up cell membranes and in the neurotransmitter acetylcholine....
, in combination with Acetyl-CoA, is catalyzed by the enzyme choline acetyltransferase
Choline acetyltransferase

Choline acetyltransferase is an enzyme that is synthesized within the body of a neuron. It is then transferred to the synapse via axoplasmic flow....
 to produce acetylcholine and a coenzyme a
Coenzyme A

Coenzyme A is a coenzyme, notable for its role in the Fatty acid metabolism#Synthesis and Fatty acid metabolism#.CE.B2-Oxidation of fatty acids, and the oxidation of pyruvic acid in the citric acid cycle....
 byproduct.

Functions


Pyruvate dehydrogenase and pyruvate formate lyase reactions

The oxidative conversion of pyruvate into acetyl-CoA is referred to as the pyruvate dehydrogenase reaction. It is catalyzed by the pyruvate dehydrogenase complex. Other conversions between pyruvate and acetyl-CoA are possible. For example, pyruvate formate lyase
Pyruvate formate lyase

FunctionPyruvate formate lyase is an important enzyme that helps regulate anaerobic glucose metabolism. Using radical chemistry, it catalysis the reversible conversion of pyruvate and coenzyme-A into formate and acetyl-CoA....
 disproportionates pyruvate into acetyl-CoA and formic acid
Formic acid

Formic acid is the simplest carboxylic acid. Its formula is hydrogencarbonoxygenOH or CH2O2. It is an important intermediate in chemical synthesis and occurs naturally, most notably in the venom of bee and ant stingers....
. The pyruvate formate lyase reaction does not involve any net oxidation or reduction.

Fatty acid metabolism

In animals, acetyl-CoA is central to the balance between carbohydrate metabolism
Carbohydrate metabolism

Carbohydrate metabolism denotes the various biochemistry processes responsible for the anabolism, catabolism and interconversion of carbohydrates in life organisms....
 and fat
Fat

Fats consist of a wide group of compounds that are generally soluble in organic solvents and largely insoluble in water. Chemistry, fats are generally ester of glycerol and fatty acids....
 metabolism (see fatty acid synthesis
Fatty acid synthesis

Fatty acids are formed by the action of fatty acid synthase from acetyl-CoA and malonyl-CoA precursors....
). In normal circumstances, acetyl-CoA from fatty acid metabolism feeds into the citric acid cycle
Citric acid cycle

The citric acid cycle ? also known as the tricarboxylic acid cycle ; the Krebs cycle; or, more rarely, the Szent-Gy?rgyi-Krebs cycle) ? is a series of enzyme-catalysed chemical reactions of central importance in all living cell s that use oxygen as part of cellular respiration....
, contributing to the cell's energy supply. In the liver
Liver

The liver is a vital organ present in vertebrates and some other animals; it has a wide range of functions, a few of which are detoxification, protein synthesis, and production of biochemicals necessary for digestion....
, when levels of circulating fatty acids are high, the production of acetyl-CoA from fat breakdown exceeds the cellular energy requirements. To make use of the energy available from the excess acetyl-CoA, ketone bodies
Ketone bodies

Ketone bodies are three water-soluble compounds that are produced as by-products when fatty acids are broken down for Energy in the liver and kidney....
 are produced which can then circulate in the blood.

In some circumstances, this can lead to the presence of very high levels of ketone bodies in the blood
Blood

Blood is a specialized bodily fluid that delivers necessary substances to the body's Cell s ? such as nutrients and oxygen ? and transports waste products away from those same cells....
, a condition called ketosis
Ketosis

Ketosis is a state characterised by elevated levels of ketone bodies in the blood, occurring when the liver converts triacylglycerol into fatty acids and ketone bodies ....
. Benign dietary ketosis can safely occur in people following low-carbohydrate diet
Low-carbohydrate diet

Low-carbohydrate diets or low-carb diets are dietary programs that restrict carbohydrate consumption usually for weight control or for the treatment of obesity....
s, which cause fats to be metabolised as a major source of energy. This is different from ketosis
Ketosis

Ketosis is a state characterised by elevated levels of ketone bodies in the blood, occurring when the liver converts triacylglycerol into fatty acids and ketone bodies ....
 brought on as a result of starvation and ketoacidosis
Ketoacidosis

Ketoacidosis is a type of metabolic acidosis which is caused by high concentrations of ketone bodies, formed by the breakdown of fatty acids and the deamination of amino acids....
, a dangerous condition that can affect diabetics.

In plants, de novo fatty acid synthesis occurs in the plastids. Many seeds accumulate large reservoirs of seed oils to support germination
Germination

Germination is the process whereby growth emerges from a period of dormancy. The most common example of germination is the sprouting of a seedling from a seed of an flowering plant or gymnosperm....
 and early growth of the seedling before it is a net photosynthetic organism. Fatty acids are incorporated into membrane lipids, the major component of most membranes.

Other reactions

  • Two acetyl-CoA can be condensed
    Condensation reaction

    A condensation reaction is a chemical reaction in which two molecules or moieties combine to form one single molecule, together with the loss of a small molecule....
     to create acetoacetyl-CoA
    Acetoacetyl-CoA

    Acetoacetyl CoA is the precursor of HMG-CoA in the the Mevalonate pathway which is essential for cholesterol synthesis. It also takes a similar role in the ketone bodies synthesis pathway of the liver....
    , the first step in the HMG-CoA/ mevalonic acid pathway leading to synthesis of isoprenoids. In animals HMG-CoA is a vital precursor to cholesterol
    Cholesterol

    Cholesterol is a lipidic, waxy alcohol found in the cell membranes and transported in the blood plasma of all animals. It is an essential component of mammalian cell membranes where it is required to establish proper membrane permeability and membrane fluidity....
     and ketone
    Ketone bodies

    Ketone bodies are three water-soluble compounds that are produced as by-products when fatty acids are broken down for Energy in the liver and kidney....
     synthesis.
  • Acetyl-CoA is also the source of the acetyl group incorporated onto certain lysine residues of histone and non-histone proteins in the post-translational modification acetylation
    Acetylation

    Acetylation describes a reaction that introduces an acetyl functional group into an organic compound. Deacetylation is the removal of the acetyl group....
    , a reaction catalyzed by acetyltransferases.
  • In plants and animals, cytosolic acetyl-CoA is synthesized by ATP citrate lyase
    ATP citrate lyase

    ATP citrate lyase is an enzyme that represents an important step in fatty acid biosynthesis....
     . When glucose is abundant in the blood of animals, it is converted via glycolysis
    Glycolysis

    Glycolysis is the metabolic pathway that converts glucose, C6H12O6, into pyruvate, C3H5O3-....
     in the cytosol
    Cytosol

    The cytosol or intracellular fluid is the liquid found inside cell . In eukaryotes this liquid is separated by cell membranes from the contents of the organelles suspended in the cytosol, such as the mitochondrial matrix inside the mitochondrion....
     to pyruvate, and thence to acetyl-CoA in the mitochondrion. The excess of acetyl-CoA
    Acetyl-CoA

    Acetyl-CoA is an important molecule in metabolism, used in many biochemical reactions. Its main use is to convey the carbon atoms within the acetyl group to the citric acid cycle to be oxidation for energy production....
     results in production of excess citrate
    Citrate

    A citrate can refer either to the conjugate base of citric acid, , or to the esters of citric acid. An example of the former, a salt is trisodium citrate; an ester is triethyl citrate....
    , which is exported into the cytosol to give rise to cytosolic acetyl-CoA.
  • Acetyl-CoA can be carboxylated in the cytosol by acetyl-CoA carboxylase
    Acetyl-CoA carboxylase

    Acetyl-CoA carboxylase is a biotin-dependent enzyme that catalyzes the irreversible carboxylation of acetyl-CoA to produce malonyl-CoA through its two catalytic activities, biotin carboxylase and carboxyltransferase ....
    , giving rise to malonyl-CoA
    Malonyl-CoA

    Malonyl-CoA is a coenzyme A derivative....
    , a substrate required for synthesis of flavonoids and related polyketides, for elongation of fatty acids to produce waxes, cuticle
    Cuticle

    In biology, a cuticle or cuticula is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or part of an organism, that provide protection....
    , and seed oils in members of the Brassica
    Brassica

    Brassica is a genus of plants in the mustard family . The members of the genus may be collectively known either as cabbages, or as mustards....
     family, and for malonation of proteins and other phytochemicals .
  • In plants, these include sesquiterpene
    Sesquiterpene

    Sesquiterpenes are a class of terpenes that consist of three isoprene units and have the molecular formula C15H24. Like monoterpenes, sesquiterpenes may be acyclic or contain rings, including many unique combinations....
    s, brassinosteroid
    Brassinosteroid

    Brassinosteroids are a group of steroidal plant hormones. Brassinolide was the first of these steroid compounds discovered in 1973, when it was shown that pollen from Brassica napus could promote stem elongation and cell divisions and that the biologically active molecule was a steroid that the authors called Brassins....
    s (hormones), and membrane sterol
    Sterol

    Sterols are an important class of organic molecules. They occur naturally in plants, animals and fungi, with the most familiar type of animal sterol being cholesterol, which has been shown to contribute to high blood pressure and heart disease....
    s.


See also

  • Citric acid cycle
    Citric acid cycle

    The citric acid cycle ? also known as the tricarboxylic acid cycle ; the Krebs cycle; or, more rarely, the Szent-Gy?rgyi-Krebs cycle) ? is a series of enzyme-catalysed chemical reactions of central importance in all living cell s that use oxygen as part of cellular respiration....
  • HMG-CoA reductase pathway
    HMG-CoA reductase pathway

    The mevalonate pathway or HMG-CoA reductase pathway or mevalonate-dependent route or isprenoid pathway, is an important cell metabolic pathway present in all higher eukaryotes and many bacteria....
  • Fatty acid metabolism
    Fatty acid metabolism

    Fatty acids are an important source of energy for many organisms. Excess glucose can be stored efficiently as fat. Triglycerides yield more than twice as much energy for the same mass as do carbohydrates or proteins....
  • Acyl CoA
  • Acetyl Co-A synthetase
    Acetyl Co-A synthetase

    Acetyl Co-A synthetase is an enzyme involved in metabolism of carbon sugars. It is in the ligase class of enzymes, meaning that it catalyzes the formation of a new chemical bond between two large molecules....
  • Malonyl-CoA decarboxylase
    Malonyl-CoA decarboxylase

    Malonyl-CoA decarboxylase is an enzyme associated with Malonyl-CoA decarboxylase deficiency.It catalyzes the conversion of malonyl-CoA into acetyl-CoA and carbon dioxide....


External links